Safety, Technical Description, and Accuracy
10-26
ACUSON Cypress™ Operator’s Manual
Accuracy of Primary Measurements
TABLE 55.
Accuracy of Primary Measurements
Measurement
Description
Distance
The system assumes that the speed of sound is 1540
meters per second and that this speed is homogeneous in all
tissues. The diagnostic ultrasound literature states that dif-
ferences in the speed of sound in the body do exist because
of the differing tissue types. In
Clinical Sonography – A Prac-
tical Guide
, (2nd Edition, Roger C. Sanders, ed., Little Brown
and Company, 1991), the range is cited as from 1500 to
1600 meters per second. These differences would produce
an inaccuracy of up to ± 4%.
The distance measurements on the system are verified
using an
AIUM
standard phantom with a fluid having an
acoustic speed of approximately 1540 meters per second at
room temperature. The accuracy of this measurement is ±
5%. The maximum range of this measurement is 24 cm.
Velocity
The velocity measurement is calibrated using a Doppler
string phantom where multiple measured velocities are
checked against actual velocities over the range of velocity
values provided by the Cypress system. The accuracy of this
measurement is ± 7%. The maximum range of this measure-
ment is 16 meters per second.
Time
The time calibration is performed using a calibrated time-
interval waveform generator.The accuracy of this measure-
ment is ± 2.5%. The maximum range of this measurement is
4 seconds.
Heart Rate
The heart rate measurement calibration is performed using a
calibrated electrocardiogram signal generator. The accuracy
of this measurement is ± 2.5%. The maximum range of this
measurement is 300 beats per minute.
